Telephone system



L. C. BYGRAVE ANI)` T. M. iNMAN. TELEPHONE SYSTEM.

APPLICATION FILED IuLv 25.1911.

Patented June 8, 1920.

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TELEPHONE SYSEM.

APPLICATION HLED luLY 25, 1911.

Patentd June 8, 1920.

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UNITED STATES PATENT OFFICE.

LEONARD CHARLES BYGRAVE AND THOMAS MON TAGU INMAN, OF LONDON, ENGLAND, ASSIGNORS TO THE RELAY AUTOMATIC TELEPHONE COMPANY, LIMITED, 0F LON- DON, ENGLAND.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented J une 8, 1920.

Application led July 25, 1917. Serial No. 182,670.

To all lwhom t may concern:

Be it known that we, LEONARD CHARLES BYGRAVE and THOMAS MONTAGU INMAN, subjects of the King of Great Britain, and residents of Marconi House, Strand, London, England, have invented a new and useful Improvement in Telephone Systems, of which the following is a specification.

This invention refers to automatic and semi-automatic telephone systems having a three digit final connecting group, and particularly to the final connecting stage thereof.

Owing to the economy and efficiency of grouping trunk lines in largegroups, attempts have been made to use larger switches than those for 100 and 200 subscribers lines, which are well known, but owing to cost and complexity these have not been adopted. This invention, however, provides a simple and economical means of giving a group of trunk lines access to large groups of subscribers, and the invention is described in connection with access to groups of 1000 lines. Such a large group must necessarily be associated with 3-digit calling, hundreds, tens and units, and preferably a plurality of common 3-digit impulse responders or selectors is provided to receive the dial impulses and complete initial lenergizing @circuits in sub-groups to correspond with the digits called, but these responders form no part of this invention. In a 10,000 line system the subscribers calling line may be arranged in any well known manner, for example, as in United States Patent No. 1234610, these lines having access vby preselectors or line switches to first selector switches which extend a calling line on the first set of digit impulses to a particular group of 1000 lines, for example, as in United States Patents Nos. 1162556 and 1195771. Our invention relates to switching devices involved in the subsequent completion of the connection in response to hundreds, tens and units impulses transmitted by the caller to connect his line with a particular line desired. The common impulse responding device and initially energizing arrangements for selecting one line in a group of 1000 may be such as described in United States Patent No. 1129543.

Figure 1 of the drawings is a schematic diagram illustrating the invention and Fig.

2 is a circuit diagram which, for the sake of simplicity, is restricted to those parts o nly of Fig. 1 which are shown in heavy lines.

As shown in Fig. 1, a connection is com pleted over a succession of small switching u nits. Connecting circuits are indicated by single lines, and 'the connecting points are indicated by Xs at the intersections of lines. The group of trunks necessary to carry the trafiic to the group of subscribers is divided into a number of sub-groups, and three sets of intermediate lines, which may be known as first, second and third intermediate lines, have each asimilar number of sub-groups, and a circuit in each sub-group is joined together to complete a connection.

Each line of a trunk sub-group a, c or d, has access to all the lines in a subgroup of first intermediate lines a', c or d. Each first intermediate line has access to one line in each sub-group of second intermediate lines a2, b2, 02, cl2, and each line in each sub-group of second intermediate lines has access to all the lines of a subgroup of third intermediate lines a3, b3, o3 or cl3.

A group of subscribers lines that may be called is shown at s l, 2, 3, 4, 5, each subscribers line being capable of connecting with six intermediate lines a4, a5, 54, c4, c5, (Z4, which are extensions of the third intermediate lines a3, b3, c3, (Z3. The six intermediate lines to which any subscribers line has access may be connected to the third intermediate lines as best suits trafiic requirements. By such an arrangement of lines, it is possible for any incoming trunk in sub-groups cz, Z), c,- d, to connect with any subscribers lines in a group of 1000 lines, such as s l, 2, 3, 4, 5.

Fig. 2 shows the operating circuits for such a system. For the simplification of the diagram only the third conductors are shown. The connecting relays would, of course, carry the usual two line wires of the talking circuit.

Only two sub-groups of trunks and intermediate lines are shown in Fig. 2, the trunk groups being A, B; the first intermediate line groups A', B; the second intermediate line groups A2, B2; and the third A3, B3; the intermediate lines extended to subscribers units A4, A*i and B. The subv scribers lines are shown at S1,'S2, S3. When a 'subscriber in a group of 1000 lines is called, the apparatus that responds to the dial impulses energizes, and directly, or through interposed apparatus, completes initial energizing circuits. In Fig. 2 it isassumed that four circuits have been completed or partly completed in this way.

Circuiti is completed to connect the common side of all relays e to earth, so that they energize. A relay e is associated with each first intermediate line f the sub-group A. If all lines of a sub-group are idle, `all relays `e of that sub-group energize.

Circuit 2 is completed to energize the incoming test relay f of the sub-group of subscribers. This connects the third conductors of certain third intermediate lines to the test relays g of the subscribers subgroup. n

Circuit 3 has battery connected to the free wire of S1 (if that subscriber as called) so that when a test relay g energizes, the corresponding connecting relay It will energize.

Circuit 4 has earth connected to the `free wire of the trunk over which a call is being made, so that a connecting relay 1l may be energized when relays e and a particular relay j have energized to nd an idle intermediate line. The relays e when energized each connect a wire in-eachl sub-group of irst intermediate lines to a relay j and batter Circuit 5 is completed and relays 7c', m2, n' and g energize. 7c momentarily opens the circuit of other relays lc to prevent interference. j energizing completes circuit 4 so that the connecting relay z" is energized to connect the calling. trunk to a first intermediate line A.

Circuit 6: j and c energizing complete a,

circuit in which the connecting relay o is initially energized to extend a line A to a second intermediate line A2.

Circuit 7: la and m2 energizing complete a circuit in which the connecting relay p' is initially energized to extend a line A2 to a third intermediate line A3. Relay g energizing completes circuit 3 to cause the connecting relay la. to extend the line A3 to the wanted subscribers line S.

Circuit 8 is the retaining or holding circuit of the completed connection, in which connecting relays i', o', p', h', are maintained energized; the cut-off relays g', r2.1?, u', fv. are energized and maintained with relay n which cuts in relay u. g causes e and y" to denergize to open the initial ener` gizing circuits of relays z' and also the circuits 5 and 6. r energizing cut off 7c so that a second call in the same sub-group will energize 702. t2 energizing opens the test circuit 5, so that the circuit tests busy when relays g are connected up by f. u energizing-v cuts off g so that g2 is takenfor the next call. 'v' is the cut-oi relay of the called partys line.

The same, calling trunk can obtain connection with the same party by any of the sub-groups of intermediate lines, as pointed out in connection with Fig. l. The calling trunk, in the connection described, can initiate a connection throughany of the relays e; each relay e can extend the connection to any intermediate line of its particution-with the testing device associated with the called subscribers line sub-group will select a particular third intermediate line to be connected withl the called party.

What we claim is f 1. In an automatic telephone system having a iinal connecting group adapted to be operated by-more than two digits, the combination of a group of trunks, a group of subscribers lines, a plurality of greater than two of sets of intermediate lines arranged with the sets in series between the trunks and subscribers lines in the final connecting group and means for connecting a trunk to a subscribers line through lines of all the sets in series.

2. In an automatic telephone system having a final connecting group adapted to be operated by more than two digits, the combination of a group of trunks, a group of subscribers lines, a' plurality greaterthan two of sets of intermediate lines arranged with the sets in series between the trunks and subscribers vlines in the final connecting group and means for connecting a trunk to a subscribers line through lines of all the sets in series, no intermediate line being capable of being taken into engagement unless it can form part of a completed connection. l

3. In an automatic telephone system having a final connecting group adapted to be operated by more than twodigits, the combination of a group of trunks, ai group of subscribers lines, a plurality greater than two of sets lof intermediate lines arranged with the sets in series between the trunks and subscribers lines in the final connecting group and means for connecting a trunk to a subscribers line through lines of all the sets in series in which only those connecting means by which a through connection can be completed are operable.

4. In an automatic telephone system having a three digit inal connecting group, the combination of a group of trunks, a group of subscribers lines, a plurality greater than two of sets of intermediate lines arranged with the sets in series between the trunks and subscribers lines and means for connecting a trunk to a subscribers line through lines of all the sets in series in which the connecting means between the various intermediate lines concerned in a connection are all operated simultaneously.

lar sub-group, and the latter in' conjunc- 5. In an automatic telephone system having a final connecting 'group adapted to be operated by more than two digits, the combination of a group of trunks, a group of subscribers lines, a plurality greater than two of sets of intermediate lines arranged with the sets in series between the trunks and subscribers lines in the final connecting group, means for connecting a trunk to a subscribers line through lines of all the sets in series and a temporary testing circuit adapted to cause the connecting means to be operated if the connection can be completed through them.

6. In an automatic telephone system having a three digit final connecting group, the combination of a group of trunks, a set of -first intermediate lines divided into subgroups, means for connecting any trunk to any one of the first intermediate lines of a sub-group, a set of second intermediate lines divided into sub-groups, means for connecting any first intermediate line to a line of any one sub-group of second intermediate lines, a set of third intermediate lines divided into sub-groups, means for connecting any second intermediate line to any of the third intermediate lines of a sub-group and a group of subscribers lines, each subscribers line having access to one line of each of a plurality of the sub-groupsof third intermediate lines.

7. In an automatic telephone system having a three digit final connecting group, the combination of a group of trunks, a set of first intermediate lines divided into subgroups, means for connecting any trunk to any one of the first intermediate lines of a sub-group, a set of second intermediate lines divided into sub-groups, means for connecting any first intermediate line to a line of any one sub-group of second intermediate lines, a set of third intermediate lines divided into sub-groups, means for connecting any second intermediate line to any one of the.third intermediate lines of a sub-group, a group of subscribers lines, eaclh subscribers line having access to one line of each of a plurality of the sub-groups of third intermediate lines and means for renderingI inaccessible any intermediate line 1ncapable of forming part of a particular connection between a trunk and a subscribers line.

8. In an automatic telephone system having a three digit final connecting group, the combination of a group of trunks, a set of first intermediate lines divided into subgroups, means for connecting any trunk to any one of thevfirst intermediate lines of a sub-group, a set of second intermediate lines divided into sub-groups, means for connecting any first intermediate line to a line of any ne sub-group of second intermediate lines, a set of third intermediate lines divided. into sub-groups, means for connecting any second intermediate line to any one of the third intermediate lines of a sub-group, a group of subscribers lines, each subscribers line having access to one line of each of a plurality of the sub-groups of third intermediate lines and means for initially completing two temporary circuits to establish connection between a calling line and a called line. 1

9. In an automatic telephone system having a three digit final connecting group, the combination of a group of trunks, a set of first intermediate lines divided into subgroups, means for connecting any trunk to any one of the first intermediate lines of a sub-group, a set of second intermediate lines divided into sub-groups, means for connecting any first intermediate line to a line of any one sub-group of second intermediate lines, a set of third intermediate lines divided into sub-groups, means for connecting any second intermediate line to any one of the third intermediate lines of a sub-group, a group of subscribers lines, each subscribers line having access to one line of each of a plurality of the sub-groups of third intermediate lines, means for initially completing two temporary circuits to establish connection between a calling line and a called line and means for establishing circuits to maintain the connection when the temporary cir- Cuits are released.

In testimony that we claim the foregoing as our invention we have signed our names this 29th day of June, 1917.

LEONARD CHARLES BYGRAVE. THOMAS MONTAGU INMAN. 

